Continuous optical null tracking method for optical switch

A method and apparatus are provided for real-time correction of a voltage drift of an optical switch. The correction may be made without interrupting an optical data stream of the optical switch. Three voltage states of the optical switch may be monitored continuously to determine whether a voltage drift has occurred. Upon determining that the voltage drift has occurred, a signal processing unit with voltage correction circuitry may apply a voltage to a single port of the optical switch to adjust the three voltages of the optical switch equally to achieve a minimum null signal. The technique may be extended to adjust a voltage drift of multiple optical switches connected in series.